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Control System B-5
MN1901
B.2 Control system operation
The following sections describe the operation of the position, speed and torque controllers.
B.2.1 Position controller
The position controller, shown below, is a typical propor in derivative (PID)
controller, with gains set by the Mint keywords
KPROP
,
KINT
and
KDERIV
. The position
demand from the profiler is compared with the measured position and the error is fed into the
PID control calculation. The resulting value forms the basic speed or torque demand,
depending on the
CONFIG
setting. The effect of the integral term can be changed using the
KINTLIMIT
and
KINTMODE
keywords.
KINTLIMIT
sets the maximum value of the effect of
integral action, as a percentage of the full scale demand.
KINTMODE
can be used to specify
the circumstances under which the integral term is applied.
As an alternative to the derivative term, a velocity feedback term is available by setting
keyword
KVEL
. To improve the tracking performance of the position controller, the profiler
speed is fed forward, by gain
KVELFF
, to give a contribution to the final speed or torque
demand. Likewise, if
CONFIG
is set to
_cfTORQUE_SERVO
, the profiler acceleration is fed
forward by gain
KACCEL
to give a contribution to the final speed or torque demand. The
position control calculation is performed every 500
μ
s.
The gain values
KPROP
,
KINT
,
KDERIV
,
KVEL
,
KVELFF
and
KACCEL
must be tuned for each
application. This can either be performed automatically within the Commissioning Wizard, or
manually using the Fine-tuning tool in Mint WorkBench.
KVELFF
KACCEL
KPROP
KINT
KDERIV
KVEL
dt
d
dt
Following
error
(FOLERROR)
Proportional gain term
Integral gain term
Derivative gain term
Velocity feedback
term
Measured speed
(VEL)
Speed or torque demand
Measured position
(POS)
Velocity feedforward term
Acceleration feedforward term
(CONFIG _cfTORQUE_SERVO only)
Profiler acceleration
Profiler speed
(VELDEMAND)
Profiler position
(POSDEMAND)
+
+
+
+
+
+
+
+
-
-
Figure 58 - Position control system
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